Consider supporting Lambda payload version 2.0

[lukelafountaine]

With the introduction of APIGW HTTP APIs, a new version of the payload format between APIGW and Lambda was also introduced - version 2.0 [1]. The serverless framework by default uses version 1.0 when an HTTP API is created. This preserves backward compatibility if switching over from using a REST API. The new format has changes to multi-value headers, the request context object and some others noted here [2]. We might want to consider supporting payload version 2.0. At this point, the need is not urgent as we can continue using v1.0 even with HTTP APIs.

[1] https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-lambda.html
[2] https://medium.com/@lancers/amazon-api-gateway-explaining-lambda-payload-version-2-0-in-http-api-24b0b4db5d36